【作者】 刘会彬；

【导师】 裴先治；

【作者基本信息】 长安大学 ， 构造地质学， 2007， 硕士

【摘要】 西秦岭北缘新阳—元龙大型韧性走滑剪切带位于甘肃省天水地区渭河流域,地处青藏高原东北缘,其大地构造位置处于中央造山系中段祁连造山带和北秦岭造山带的接合部位,同时也横跨在中国中部贺兰山—川滇南北向构造带上,是古亚洲构造域、特提斯构造域和太平洋构造域复合叠加的构造部位。祁连—北秦岭造山带的衔接、过渡、转换、交接部位,既有相似、共同之处,也有许多差异与独特之处,这对于深入研究华北板块与扬子板块之间聚合与离散的多期复合造山过程、造山带接合部位组成、结构、构造、演化与造山机制的转换以及造山过程与动力学等一系列涉及中国大陆大地构造格架及其演化、大陆造山带和大陆动力学等重大基础地质问题,具有十分重要的科学意义。通过对剪切带及其糜棱岩的几何学、运动学、构造岩石学、矿物学、同位素年代学方面的研究,确定:1、研究区平面构造几何学样式和地层分布特征表明秦岭（主要是西秦岭）与祁连造山带之间不是简单的连通对应关系,而是呈巨大的斜切交接关系,接合部位为新阳—元龙大型右行韧性走滑剪切带,划分了祁连—秦岭两个一级构造单元;2、根据糜棱岩矿物学、矿物变形特征、矿物组合特征以及构造岩组学特征,结合区域地层、区域构造和岩浆岩分布特点认为剪切带形成于中浅构造层次（＜15km）的中压低温绿片岩相环境,压力约6kb,温度约350～450℃;3、对剪切带中花岗质糜棱岩进行了锆石LA-ICP-MS U-Pb同位素年龄测定,确定花岗质糜棱岩原岩结晶年龄为XYZ08=（935.5±3.1Ma）、XYZ07=（978.5±4.8Ma）、YL02=（914.7±7.6 Ma）,原岩为新元古代（晋宁期）华北和扬子板块俯冲-碰撞构造岩浆热事件的产物;4、祁连—秦岭造山带接合部位为一个构造复合叠加的地区,经历了多期多层次构造运动的影响,构造复杂,根据区域地层和区域构造特征,结合前人黑云母⁴⁰Ar/³⁹Ar同位素年代学研究成果确定剪切带形成于早石炭世,为海西运动的产物,表明祁连—秦岭早古生代处于走滑拼贴构造环境;5、根据区域地质演化特征研究认为祁连—秦岭造山带接合部位共经历了5期构造作用:①古元古代造山带变质基底形成演化;②中新元古代过渡性基底形成演化阶段,晋宁期华北与扬子古陆拼合;③早古生代板块构造演化与加里东期俯冲—碰撞造山;④晚古生代—三叠纪板内伸展裂陷与祁连—秦岭造山带斜向碰撞走滑拼贴;⑤中新生代陆内演化为主,表现为脆性断裂的剪切走滑、断块活动、山体隆升、盆地沉降。更多还原

【Abstract】 Xinyang-Yuanlong Larger scale Ductile Strike-Slip Shear Zone（XYDSZ）,of the west Qinling north margin,is located in Tianshui area,Gansu province,and also lies in the NE margin of the Qinghai-Tibet Plateau,the geotectonic Setting lies at the junction of the Qilian orogenic belt and the North Qinling orogenic belt of the middle section of the Central Orogenic System of China,and also stretches over the S-N（Helanshan-Sichuan-Yunnan） tectonic belts in the central area of China,It occupies a superposed tectonic position,which is overlapped by the paleo-Asiatic tectonic domain,the Tethyan tectonic domain and the Pacific tectonic domain.Because it lies at the junction,the transition,transformation and connection sections of the Qilian orogenic belt and the Qinling orogenic belt,this region not only presents similarities with the two orogenic belts,but also many differences from them It is of vital scientific significance for us to study the multi-phase orogenic processes between the convergence and divergence of the North China plate and the Yangtze plate,the composition, configuration,structure,evolution and transformation of orogenic mechanism at the junction of orogenic belt position,also orogenic process and the dynamics,etc.All these involve a significant foundation for the geological issues of the China continental geotectonic framework and evolution,the continental orogenic belt and continental dynamics.According to the geometry,kinematics,structural petrology,mineralogy,isotopic chronology etc.researches which can gain some conclusions as below:1,That the plane structural geometry pattern and the distribution of stratum of research field indicated that the Qinling and Qilian are not simply connected and corresponded with each other,but the structural relationship showed a huge juxtaposition and conjoin. Xinyang-Yuanlong Shear Zone of the junction is a lager dextro-rotational ductile strike-slip shear zone,which subdivided both Qilian and Qinling structural units;2,According to the granitic mylonite’s mineralogy,,microstructure,structural fabric and mineral assemblage characteristic,and integrating stratigraphy,regional geology and magmatic rock distribution suggested that the shear zone formed from middling-superficial level（＜15km） in mid-pressure-low-temperature greenschist facies,the pressure about 6kb,the temperature about 350-450℃;3,The LA-ICP-MS U-Pb zircon isotopic dating of granitic mylonites was carded out, which confirmed the ages are XYZ08=（935.5±3.1Ma）,XYZ07=（978.5±4.8Ma） and YL02 =（914.7±7.6 Ma ） of the protolith,which are the neoproterozoic（Jinningian） products of the North China block and Yangtze block subduction-collision tectonic-magmatic thermal event;4,The Qilian and Qinling orogenic belts’s junction is a complex overlay tectonic region undergone complexly differ times and levels tectogenetic influence.Based on stratigraphy and areal structure characteristic,and integrated,the biotite（⁴0）Ar/³⁹Ar isotopic dating results of predecessors confirm that the shear,zone,formed from lower carboniferous,was the hercynian movement result,which indicated Qilian-Qinling on strike-slip collage tectonic setting during eopaleozoic era;5,According the areal geology evolvement characteristic researches suggested the Qilian and Qinling belts’s junction undergone five times major tectonic movements:①Paleoproterozoic Era is the metamorphosed basements formed and evolved stage;②Meso-neoproterozoic transition basements formed and evolved stage,Jinningian the North China block and Yangtze block were converged;③Eopaleozoic was the block structure evolve and Caledonian subduction-collision stage;④The intraplate extensional tectonics and the Qilian-Qinling orogenic belts’s oblique collision strike-slip collage were occurred in Neopaleozoic-Triassic stage;⑤In Neozoic-Cenozoic stage mostly happened the intracontinental evolvement,which behaved as brittle fractural shear strike-slip,fault block activities,mountains uplift,basin subsidence.更多还原